Backlight module with means for fixing circuit board to light guide plate

ABSTRACT

An exemplary backlight module ( 5 ) includes a light guide plate ( 54 ) having a light incident surface ( 546 ), and a circuit board ( 62 ) disposed adjacent to the light incident surface. A pair of protrusions ( 544 ) of the light guide plate engages in a pair of fixing holes ( 524 ) of the circuit board, thereby fixing the circuit board and the light guide plate together. The backlight module may further include one or more optical films. In such case, the above-described fixing means may further include a plurality of side-blocks or a plurality of corner-blocks integrally formed on a light emitting surface of the light guide plate. The side-blocks or corner-blocks enable the optical films to be tightly held on the light guide plate without gaps therebetween.

FIELD OF THE INVENTION

The present invention relates to backlight modules, and especially to abacklight module for liquid crystal display (LCD) devices.

BACKGROUND

Liquid crystal displays are commonly used as display devices for compactelectronic apparatuses, because they not only provide good qualityimages with little power but also are very thin. The liquid crystals ina liquid crystal display do not emit any light themselves. The liquidcrystals have to be lit by a light source so as to clearly and sharplydisplay text and images. Thus, a backlight module for an LCD isgenerally needed.

FIG. 9 is a schematic, exploded view of a conventional backlight module.The backlight module 1 includes two prism films 16, a diffusing film 15,a light guide plate 14, a plastic frame 17, a reflective film 13, and abottom tray 18 arranged top to bottom in that order. The light guideplate 14 includes a light incident surface 141, and a light emittingsurface 142 adjoining the light incident surface 141. The diffusing film15 and the prism films 16 are disposed adjacent to the light emittingsurface 142 of the light guide plate 14. The backlight module 1 furtherincludes a flexible printed circuit (FPC) 12, and three light emittingdiodes (LED) 11 connected with the FPC 12. The FPC 12 provides power forthe LEDs 11. The LEDs 11 are disposed adjacent to the light incidentsurface 141 of the light guide plate 14. Light beams emitted by the LEDs11 enter the light guide plate 14 through the light incident surface141, and then are emitted from the light emitting surface 142.

The FPC 12 is arranged adjacent to the light incident surface 141 of thelight guide plate 14, and the diffusing film 15 and the prism films 16are arranged on the light emitting surface 142 of the light guide plate14. It is difficult to obtain an exact fit when assembling the FPC 12,the diffusing film 15, and the prism films 16 together. Further, even ifa compact assembly is attained, the assembly may loosen and becomeunstable when the backlight module 1 is used.

What is needed, therefore, is a backlight module in which the FPC andoptical films thereof are compactly and stably assembled together,preferably without any gaps therebetween.

SUMMARY

In at least one preferred embodiment, a backlight module includes alight guide plate having a light incident surface, a circuit boarddisposed adjacent to the light incident surface, one or more opticalfilms stacked on the light guide plate, and a fixing means securing thecircuit board, the light guide plate and the optical films together.

The fixing means can firmly fix the light guide plate, the circuit boardand the optical films together. Thereby, gaps between the optical filmsand the light guide plate can be avoided.

Other advantages and novel features will become more apparent from thefollowing detailed description of preferred embodiments when taken inconjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, isometric view of a backlight module according toa first embodiment of the present invention;

FIG. 2 is an assembled view of the backlight module of FIG. 1;

FIG. 3 is an exploded, isometric view of a light guide plate and acircuit board of a backlight module according to a second embodiment ofthe present invention;

FIG. 4 is an exploded, isometric view of a light guide plate and acircuit board of a backlight module according to a third embodiment ofthe present invention;

FIG. 5 is an isometric view of a light guide plate of a backlight moduleaccording to a fourth embodiment of the present invention;

FIG. 6 is similar to FIG. 5, but showing a circuit board attached ontoan end of the light guide plate;

FIG. 7 is an isometric view of a light guide plate of a backlight moduleaccording to a fifth embodiment of the present invention;

FIG. 8 is similar to FIG. 7, but showing a circuit board attached ontoan end of the light guide plate; and

FIG. 9 is an exploded, isometric view of a conventional backlightmodule.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made to the drawings to describe the preferredembodiments in detail.

FIG. 1 is an exploded, isometric view of a backlight module according toa first embodiment of the present invention. The backlight module 2includes two prism films 26, a diffusing film 25, a light guide plate24, a plastic frame 27, a reflective film 23, and a bottom tray 28arranged in that order. The light guide plate 24 includes a transparentsheet 241 and two ears 242. The transparent sheet 241 includes a lightincident surface 246, and a light emitting surface 248 adjoining thelight incident surface 246. Each ear 242 extends from a respective endof the light incident surface 246, and includes a protrusion 244. Thediffusing film 25 and the prism films 26 are arranged adjacent to thelight emitting surface 248.

The backlight module 2 further includes a circuit board 22, and threelight emitting diodes (LED) 21 arranged on the circuit board 22. Thecircuit board 22 can be a flexible printed circuit (FPC) or a printedcircuit board (PCB), and provides power for the LEDs 21. The LEDs 21 aredisposed adjacent to the light incident surface 246 of the light guideplate 24. The circuit board 22 is adjacent to the light guide plate 24at the light incident surface 246, with part of the circuit board 22overlapping the light emitting surface 248. The circuit board 22 definestwo fixing holes 224 corresponding to the protrusions 244.

FIG. 2 is an assembled view of the backlight module 2. The protrusions244 are engaged in the fixing holes 224, thereby firmly fixing thecircuit board 22 and the light guide plate 24 together.

FIG. 3 is an exploded, isometric view of a light guide plate 34 and acircuit board 32 of a backlight module 3 according to a secondembodiment of the present invention. The light guide plate 34 includes alight incident surface 341, and a light emitting surface 342 adjoiningthe light incident surface 341. Two protrusions 344 are integrallyformed on two corners respectively of the light emitting surface 342that are adjacent to the light incident surface 341. The circuit board32 defines two fixing holes 324 corresponding to the protrusions 344.The protrusions 344 are engagingly received in the fixing holes 324,thereby firmly fixing the circuit board 32 and the light guide plate 34together.

FIG. 4 is an exploded, isometric view of a light guide plate 44 and acircuit board 42 of a backlight module 4 according to a third embodimentof the present invention. The circuit board 42 defines two fixing holes424 in two ends thereof respectively. The light guide plate 44 includesa light incident surface 441, and a light emitting surface 442 adjoiningthe light incident surface 441. The light guide plate 44 defines twofixing holes 444 in two corners thereof that are adjacent to the lightincident surface 341 respectively. The fixing holes 444 correspond tothe fixing holes 424. The backlight module 4 further includes twofasteners such as bolts 426. The bolts 426 are engaged in the fixingholes 424, 444, thereby firmly fixing the light guide plate 44 and thecircuit board 42 together.

Referring to FIG. 5 and FIG. 6, a backlight module 5 according to afourth embodiment of the present invention includes a light guide plate54 and a circuit board 52. The light guide plate 54 includes atransparent sheet 541, two ears 542, and four L-shaped corner-blocks545. The transparent sheet 541 includes a light incident surface 546,and a light emitting surface 548 adjoining the light incident surface546. Each ear 542 extends from a respective end of the light incidentsurface 546, and includes a protrusion 544. The circuit board 52 definestwo fixing holes 524 corresponding to the protrusions 544 of the lightguide plate 54. The L-shaped corner-blocks 545 are disposed at fourcorners respectively of the light emitting surface 548. The backlightmodule 5 typically also includes a plurality of optical films (notshown) disposed on the light emitting surface 548 of the light guideplate 54. The L-shaped corner-blocks 545 facilitate firm fixing of thecircuit board 52 and the light guide plate 34 together, and also enablethe optical films to be tightly held on the light guide plate 54 withoutgaps therebetween. The transparent sheet 541, the protrusions 544, andthe L-shaped corner-blocks 545 are integrally formed together.

Referring to FIG. 7 and FIG. 8, a backlight module 6 according to afifth embodiment of the present invention includes a light guide plate64 and a circuit board 62. The light guide plate 64 includes a lightemitting surface 648, two protrusions 644, and two side-blocks 646 Theside-blocks 646 extend perpendicularly upwardly from two oppositelateral sides of the light emitting surface 648 respectively. Thecircuit board 62 defines two fixing holes 624 corresponding to theprotrusions 644. The backlight module 6 further includes an optical film662 disposed on the light emitting surface 648 of the light guide plate64. The optical film 662 defines two cutouts (not labeled) in oppositelateral sides thereof respectively, the cutouts corresponding theside-blocks 646. The light guide plate 64, the circuit board 62, and theoptical film 662 are firmly fixed together by way of the protrusions 644being engagingly received in the fixing holes 624, and the side-blocks646 being engagingly received through the cutouts.

The side-blocks 646 and the cutouts enable the optical film 662 to betightly held on the light guide plate 64 without gaps therebetween.

In alternative embodiments, the light guide plates 24, 34, 44, 54, 64and the circuit boards 22, 32, 42, 52, 62 can be configured with groovesand protrusions respectively, with the grooves of the light guide plates24-64 engagingly receiving the protrusions of the circuit boards 22-62.In further alternative or supplementary embodiments, the light guideplates 24-64 and the circuit boards 22-62 can be respectively fixedtogether by a bonding agent such as epoxy applied between the lightguide plates 24-64 and the circuit boards 22-62.

It is believed that the present embodiments and their advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the invention or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments of the invention.

1. A backlight module, comprising: a light guide plate having a lightincident surface, a light emitting surface adjoining the light incidentsurface; a circuit board disposed adjacent to the light incidentsurface; and a fixing means attaching the circuit board and the lightguide plate together, which comprises two ears formed with the lightguide plate, and each ear comprises a protrusion; wherein the circuitboard comprises two fixing holes corresponding to the protrusions. 2.The backlight module as claimed in claim 1, wherein the light guideplate further comprises a plurality of corner-blocks, each corner-blockbeing formed with a corner of the light emitting surface.
 3. Thebacklight module as claimed in claim 1, wherein the light guide platefurther comprises two opposite side-blocks, each side-blockperpendicularly extending from a respective side of the light emittingsurface.
 4. The backlight module as claimed in 3, further comprising anoptical film defining two notches corresponding to the side-blocks. 5.The backlight module as claimed in claim 1, wherein the fixing meanscomprises two protrusions extending from two corners of the lightemitting surface that are adjacent to the light incident surface.
 6. Thebacklight module as claimed in claim 5, wherein the circuit boarddefines two fixing holes corresponding to the protrusions.
 7. Thebacklight module as claimed in claim 6, wherein the fixing meanscomprises two fasteners.
 8. The backlight module as claimed in claim 7,wherein the circuit board and the light guide plate each define twofixing holes corresponding to the fasteners.
 9. The backlight module asclaimed in claim 1, wherein the circuit board is a flexible printedcircuit.
 10. The backlight module as claimed in claim 1, wherein thecircuit board is a printed circuit board.